Reticulated structure and method of making the same



Patented Dec. 7, 1948 RETICULATED STRUCTURE AND METHOD OF MAKING THESAME.

Anselm Talalay, New Haven, ConnQassignor to The Sponge Rubber ProductsCompany, Shelton, Conn, a corporation No Drawing. Application January26, 1946, Serial No. 643,822

4 Claims.

This invention relates to fibrous material in open-mesh or reticulatedform and comprising a -binder such as rubber or the like which anchorsat least some of the fibers to each other at their crossing positionsand also provides an elastic sheath or coating for individual fibers,and to procedure for the manufacture of such products.

Such products have various uses, including airfiltering, heat insulationand others, but they are chiefly important as cushioning material andespecially in the field of furniture upholstering and similar uses.

Heretofore it has been known to rubberize hair, such as curled hog hair,in open mesh form, as by spraying or dipping or both, and also toproduce a fiber-reinforced sponge-like material by causing a dispersionof rubber or the like to extend itself by foaming into the intersticesof an open mesh body of hair.

In such procedures, however, with hair or its equivalent as the fibrousmaterial, the range of physical properties and mechanicalcharacteristics in the product has been limited by the character of thefibrous material.

My chief object is to provide new products having desirablecharacteristics such as are not obtainable in the employment of hair asabove referred to, and especially to provide a cushioning materialcombining extremely light weight with some or all of the advantages ofstrong cushioning resistance, durability under conditions of use such asthose of a furniture cushion, for example, and effectiveness as avibration-damping material.

I find that I can attain these objects with results of quite a difierentorder from those attained in the use of even curled hair, by employing,with suitable procedural steps, natural sheep's-wool or its equivalent,as the fibrous material.

One example of the wide divergence of my invention from the prior art isthat, without using any blowing agent in, or foaming or frothing of, thebinder, but by simpler and less expensive steps, I obtain an integralcushioning body, extensive and of closely similar structure in each ofthe three dimensions, which has characteristics closely comparable tothose of a fiber-reinforced sponge rubber, but with even lighter weightfor a given cushioning resistance, durability, or shock absorbingproperty.

In the preferred procedure for the practice of my invention the fibrousmaterial, which may be either virgin or reprocessed wool or the like, is

picked on a standard textile picker and then carded out on the usualtype of carding machine,

' to produce a very thin and open-mesh web.

- The web or a small number of superimposed webs, is then sprayed withrubber latex or the like from one side and dried and then from the otherside and dried, the drying preferably being effected by passing the webunder a hot air blast. Next the web is dipped in a dilute latex or likedispersion, the surplus liquid is allowed to drain ofi and the web isagain dried.

The resulting web material is then plied up in a multiplicity of layers,a latex or other suitable cement being used for adhesion of thelaminations to one another, and in this way the structure can be builtup to any desired thickness.

The integrated mass is then treated to cause the binder to set, as byvulcanization in the case of rubber latex, and in such treatment thematerial can be subjected to suitably light molding pressure, eitherbetween flat plates to produce a slab of even thickness or in acontoured mold for producing desired shapes.

Because of the three-dimensional character of the kinks of the wool orthe like, in conjunction with the use of the adhesive, stri'ation ishardly observable in a cross-section of the product, and the mass haspronouncedly open-mesh structure in all three of the dimensions, withthebinder evenly distributed upon the fibers. f

The remarkable properties of the product are strikingly brought out bycomparison with foam rubber, which has a theoretically desirablestructure or geometrical arrangement of the substance but haslimitations in that it can not be made commercially lighter than about 4pounds per cubic foot because at lighter weight it is subject tocollapse during the jelling step and when produced in lighter weight itsstrengthagainst distortion is inadequate for supporting necessary loads.

As an example, a piece of neoprene foam of 2.8 lbs. per cu. it. wasfound to have a 50% compression resistance of only .075 lb. per sq. in.,whereas a sample of my product weighing only 2 lbs. per cu. it, had 50%compression resistance of about 0.5 lb. per sq. with a ratio of rubberto fiber of 3 to 1, being thus suitable for use as an overlay pad on aspring case of an automobile seat or of an inner-spring mattress, inspite of its extremely low weigh The surprising new results obtained arein my pinion due, with suitable procedure applied, to one or more ofseveral characteristics of..the wool or the like in which such materialsdifler vantage from the standpoint of an upholstery material. It wasfound that the vibration damping properties of a reticulated materialimprove rapidly as the mesh size is reduced.

7. The wool-reinforced product has a physical structure in which thenumbers of bonds between fibers is of a different order from that of theopenmesh rubberized fibrous materials of the prior ment of wool or, ofhair as being analogous to that of a coil spring, the ratio of filamentdiameter to "coil" diameter is less in the case of wool than in the caseof hair, and because of that, and because of the large number of kinksper inch, the strain in the wool filament, and

in its coating, is less than in the case of rubberized hair. assumingproportionate, evenly distributed coatings in the two cases, so that thecoated wool is the less subject to fatigue. At the same time. because ofthe fineness of the wool and of its kinks, and because of thethreedimensional character of the kinks in an individual wool fiber, amass of the bonded wool product has, as a whole, a strong resistance tocompressive forces in relation to its total weight, suitable procedurehaving been employed for providing a uniform disposition of the binder.

' 5. Wool is a highly elastic substance, having an elongation at breakas high as or even 50%, which puts it in a range quite different fromthat of hair.

6. W001 presents, per pound, a vastly greater surface area for receptionof the binder than hair does,so that it can receive, without theirregularity of distribution which results from over-loading, a largeramount of the binder, which is important for obtaining the desiredcharacteristics in the product without excessive weight.

' Assuming the following,

Density of wool=l.30

Density of hair=1.15 Mean diameter of wool=0.001" Mean diameter ofhair=0.006"

one pound of. wool will be represented by a single filament 265x 10 in.long, with a surface area of 83,000 sq. in. and one pound of hair by afilament 0.845x10' in. long with a surface area of 15.900 in).

The surface area available for deposition of rubber is thus in the ratioof at least 5 to 1. This is important for the production of apermanently elastic rubberized fiber space lattice. It was found that ata given total density of rubberized material, say 3 pounds per cubicfoot, 'the lasting properties of the material are directly in relationto the ratio of (evenly distributed) rubber to fiber. That is to say. amaterial made up of 2 lbs. rubber and 1 lb. of fiber (ratio 2:1) is amore permanently elastic body than one containing 1%1bs. of each (ratio1:1) and a material havi 2 lbs. rubber and /2 lb. fiber (ratio 5:1) evensurpasses the material with the ratios 3:1 or 4:1. This is conditionalupon the ability to distribute the rubber evenly throughout. Normalrubberized hair has a fiber to binder ratio of about 1:1. When weattempt to deposit more rubber on the hair, the deposition becomesdiscontinuous, i. e. globules and droplets (beads) are formed along thefibers. Thicker coats are no substitute for a greater number ofrubber-sheathed strains.

A close-mesh space lattice has yet allot tl' fi art. For analogy, thebonded wool product can be considered as substantially a macroscopicmodel of a rubber molecule, which. according to I modern teachings, ismade up of more or less coiled or kinked chains held together atselective points by cross linkages. The coiled molecules are representedby the kinked wool filaments and the linkages by latex bonded points.

An attempt can easily be made to calculate the number of cross-links inmy product as compared to a comparable weight and volume of rubberizedhair.

' Assuming in'each instance that one pound of fiber is evenlydistributed in one cubic foot of space, and that one third of allfilaments run along the 1:. the y, and the z axis, we find that 30,000times as many cross links can be expected in any given volume of mymaterial as compared with rubberized hair.

8. Each of the three wetting-and-drying operations pronouncedly inoreuesthe thickness of the web, and these successive increases of thicknessapparently are not merely the result of the addition of bonding materialto the faces of the web but apparently are in large measure due to anincrease of the three-dimensional kinkiness of the wool fibers. effectedby the wetting and drying steps, uneven shrinkage of the binder as itdries possibly being a factor. Another possible factor is that inbonding the fibers one to another at their crossing positions the liquiddispersion may space them apart at those positions by being drawn inbetween them by capillary attraction, and this factor may be large byreason of the very large number of such crossing positions in wool orthe like.

1 Whatever the reasons may be, these increases of the thickness of theweb are pronounced and, as they are cumulative, the web thickness in thefinal, laminated product is usually two or more times the originalthickness of the untreated web.

Because of the thickening of the webs in the successivewetting-and-drying operations, a cushion of appropriate thickness can bebuilt up by the stacking up of a comparatively few layers of the treatedweb material.

While I prefer to use natural wool. in its virgin iorm, including noilsor combings, or reclaimed stituted, examples being crimped, finedenierrayon, supplied by Celanese Rayon Corporation under the trade nameCelerese," and crimped casein fibers, supplied by National Dairy Products Corporation under the trade name Aralac."

Also the rubber latex can be substituted by the synthetic lattices suchas neoprene latex type 60 or type 571, GRS lattices, Buna N lattices,and artificial dispersions of reclaimed rubber. Advantages inherent insuch use of neoprene (a chloro-butadiene polymer) are that thiselastomer is fiame resistant, which, in conjunction with the good fiameresistant properties of wool. results in a final material that will notsupport combustion; that ohemical vulcanization of neoprene is notaflected by sulphur liberated by breakage of sulphur linkages in theheating of the wool; and that with neoprene as the elastomer the producthis high resistance to deterioration by oils or hydrocarbon solvents, sothat the final material is well suited for use in articles requiring tobe dry-cleaned in the course of their use.

It is not necessary to use any setting agent, as setting occurs byevaporation of water in the drying steps and the compounding techniqueis governed mainly by the requirements of good stability for storage,transport, spraying and dip ping. vulcanization is desirable but notindispensable.

It is desirable that the web or superposed webs be of well carded openstructure at the time of spraying and yet of such thickness of the massas to avoid loss of material in the striking through, and escaping intothe exhaust, of the latex. 'I'o conform to both of these considerationsthe webs can be carded very thin and a plurality of them superposedbefore they are sprayed. Also, if desired, the somewhat preferentialalignment of fiber in one direction can be compensated by crossing theindividual webs, as by the use of cross-lappers, which are well known inthe textile art.

Uniformly of deposition of the rubber or the like upon the filaments,which is highly important, as above mentioned, presents a problem in thecase of filaments which are in a 'nontwettable condition, as in the caseof natural wood which by reason of its nature or because of treatmentgiven it in textile processes, has its filaments coated with a greasy oroil-like substance.

If such wool is immersed into latex and withdrawn, a non-uniformdeposition will result. Globules will form, especially at theintersections, and leave regions which will remain uncoated.

I have found that the uniformity of distribu- 'tion can be achieved by anumber of means:

a. The wool can be completely degreased by scouring, extraction, solventwashing, or in any known or preferred manner. Thereupon a wetting agentis deposited on the wool by a spraying or dipping process, before thelatex treatment. If material so treated is sprayed with or dipped intolatex, it will exhibit a satisfactory distribution of latex on itssurface.

b. An alternative, and very successful method, is as follows:

The material, not necessarily degreased, is coated by spraying it withor dipping it in a surface coagulant.

Example of coagulant:

Parts (1) Methanol 60.0 Acetone 20.0 Calcium nitrate 12.5 Calciumchloride (dessicator grade) 12.5 (2) Methanol 80 Calcium nitrate 20Common commercial product, containing 4 molecules of water.

The coagulant is caused or allowed to drain and dry. This can be doneinany stage prior to dipc5 by the coagulative phenomenon. Thickness ofdeposit controlled by concentration of latex and time of immersion.

The procedure and the product are susceptible of variation'withoutsacrifice of all of the advantages above set out and without departurefrom the scope of the appended claims.

I claim:

1. The method of making a stereoreticulate structurev which comprisesapplying an aqueous dispersion of an elastomer to coat and bind to oneanother at their crossing positions the fibers of a three-dimensionallyopen-mesh, unwoven and unfelted web of fibrous material havingsubstantially the fiber size and kink characteristics of wool, andplying up and adhering to one another a multiplicity of laminations ofthe so treated web material, the resulting structure being thus broughtto its final condition of internal structure while in open-mesh,net-work form in all of the three dimensions, the coating and bindingbeing effected by first spraying the Web with the said dispersion anddrying it, and then dipping it in the said dispersion and drying it, andadhesion of the laminations being effected by applying an adhesive tothe sprayed, dipped and dried web material, the product by stepsdefined, being given a final ratio of elastomer to fiber greater than 2to 1 by weight.

2. A stereoreticulate structure comprising a mass of unwoven andunfelted fibrous material having substantially the fiber size and kinkcharacteristics of wool, the fibers being individually coated and bondedto one another at their crossing positions by a substance havingsubstantially the resilient deformability of soft-rubber, the structurein its final condition being of substantially the same net-work form inall of the three dimensions, and the coating and bonding substance beingdistributed with substantial uniformity upon the fibers and the ratio ofthe coating and bonding substance to the fiber being more than 2 to 1 byweight.

3. A method as defined in claim 1 in which the elastomer is achloro-butadiene polymer.

4. A structure as defined in claim 2 in which the substance with whichthe fibers are coated and bonded as defined is a chloro-butadienepolymer.

ANSELM TALALAY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number I Name Date 1,906,028 Weber et a1 Apr. 25,1933 1,988,843. Heldenbrand Jan. 22, 1935 2,057,167 Sherman Oct. 13,1936 2,341,130 Unsworth Feb. 8, 1944 FOREIGN PATENTS Number Country Date542,687 Great Britain Jan. 23, 1942 OTHER REFERENCES Ser. No. 202,136,Nottebohm (A. P. 0.), published May 11, 1943.

